Two phases of rapid loess deposition during the last deglaciation and mid-Holocene in central Sweden

Abstract

High-latitude regions are emerging as sensitive and potentially expanding sources of atmospheric mineral dust under contemporary climate warming. Aeolian activity in sub-Arctic landscapes such as Sweden during the last deglaciation may therefore act as a valuable analogue for understanding these future high-latitude dust–climate feedbacks. However, the timing and drivers of postglacial aeolian activity in Sweden remains uncertain. Furthermore, Swedish wind-blown loess deposits are thin and prone to reworking, complicating reliable age determination. Here, we combine high sampling resolution luminescence (quartz OSL, feldspar IRSL) and radiocarbon dating with complementary sedimentological, mineral magnetic and multi-proxy luminescence signal analyses to resolve postglacial–Holocene aeolian activity at Brattforsheden, Värmland. Our analyses demonstrate the value of luminescence sensitivity and portable OSL for assessing age reliability and differentiating between reworked and in situ deposits in thin loess sediments. We show that an intense but short period of postglacial-Holocene aeolian activity occurred in central Sweden immediately following deglaciation, with dust activity persisting for ~ 1500 years after regional ice retreat. We also reveal a later aeolian reworking phase linked to local fire activity at ~ 7 ka, setting new constraints on high-latitude dust dynamics under changing conditions, and implying that even during peak Holocene warmth the landscape was sensitive to aeolian reworking and dust emission could occur.